Marin transportation officials are pointing fingers at their consultants after learning some of the data supporting a proposed $143 million construction project on the Larkspur and Corte Madera stretch of Highway 101 is incorrect.

The Transportation Authority of Marin included traffic accidents from San Francisco in its collision report and changed the project area by citing different mile post markers for the project than those listed in its environmental document.

Dianne Steinhauser, TAM executive director, said these were unfortunate mistakes by the authority's contracted consultants.

"Oh my gosh, did we make a bad data entry mistake," Steinhauser said. "The consultant pulled the data and didn't pull it correctly."

She said she has no idea why the consultant recently cited the project area as being from the highway's mile-marker 7 to mile-marker 9, when the environmental document lists the project as being from mile-marker 7.2 to 8.9.

Corte Madera elected officials plan to weigh-in on the project again Monday during a special Town Council meeting. They'll be completing a letter to Caltrans detailing their problems with the project. They'll also be discussing whether to allow the closure of Nellen Drive as part of the project's southbound improvements.

Thursday is the last day to submit project comments to Caltrans.

Critics of the project claim it is outdated, too massive, inadequate for bicyclists and pedestrians and doesn't address traffic congestion on Sir Francis Drake Boulevard.

TAM already has invested $7 million on engineering, planning and environmental requirements.

Steinhauser claims the project will reduce traffic congestion, add $17 million in pedestrian and bicycle improvements and ultimately increase safety.

"Without the project, traffic conditions will become worse and congestion will increase," Steinhauser said. "Most of the accidents are related to weaving and merging."

Transportation officials said about 170,000 cars travel the Larkspur-Corte Madera stretch of Highway 101 each day, and that Sir Francis Drake Boulevard carries about 50,000 vehicles each day.

TAM officials have recently been citing collision data from 2000 to 2009, stating there were 1,195 accidents in the project area during that time. A total of 556 people were injured and two people died. This data is different from what's in the project's environmental document, which only lists data from 2007 to 2009.

At last week's meeting on the proposal, the California Highway Patrol also said the highway needs to be fixed because it's a dangerous area with a lot of collisions.

Steinhauser said the decision to use the 10-year data was made to give people a broader view of the problems on the highway.

"It doesn't conflict, it supports the conclusion of the environmental document," Steinhauser said.

TAM has said Caltrans only requires the three most recent years of collision statistics be included in the report, but said the plan is to include the 10-year data in the final environmental document.

Corte Madera Mayor Diane Furst said the new 10-year data report includes more than 150 collisions from the San Francisco area. Furst said she was looking at the records — made available to council members last week — when she noticed some of the street names were unfamiliar.

"I started getting really curious about it," Furst said. "Lo and behold, I found a ton of them."

Furst said she went through the 17 pages of data and typed the mile-marker numbers for all the locations she didn't recognize into the Caltrans Earth online map system. She discovered 159 collisions outside of the project area.

Steinhauser said those crashes weren't supposed to be included in the report.

"The team has since removed all the San Francisco accidents, but to be on the safe side we're asking Caltrans to review all the crashes," Steinhauser said. "We should hear from them next week."

The consultants who compiled the data — Matt Haynes, of Fehr and Peers, and David Parisi, of Parisi Associates — couldn't be reached for comment Friday by the Marin Independent Journal.

Furst also pointed out the two sets of collision data cite different areas of the highway by using different mile-marker numbers. The most recent data set includes two fatal accidents from 2001 and 2005, both of which Furst said appear to be related to motorists' medical problems, not traffic.

"Parameters don't change themselves," Furst said.

She and others have accused TAM of changing the data to include the two fatalities as a way to make the project seem like it's direly needed.

Steinhauser said the project doesn't hinge on whether the two fatalities are included.

Corte Madera Town Councilman Bob Ravasio said he's upset the mile-marker data was changed, but more upset the TAM board and community councils weren't advised of the alteration.

"The question we're all thinking is 'why weren't we informed of that?,'" Ravasio said.

He echoed concerns of Larkspur City Councilman Brad Marsh, who said last week that such mysterious changes lead to trust issues.

"This is a staff group that is paid by the taxpayers to present information," Ravasio said.

TAM has offered to create a seven-member committee with two representatives each from Larkspur and Corte Madera to explore project alternatives and look at previous ideas that were turned down. The remaining committee members and whether the communities even want to participate has yet to be decided.

Steinhauser said the committee would need to come up with a recommendation within about six months.

She said the millions earmarked for the project could be lost if local decision-making takes too long.

The project would be funded by the 2004 voter-approved Regional Measure 2, which increased tolls on state bridges by $1 for transportation improvement projects. TAM has also committed gas tax revenue to the project.

"We don't have a huge amount of time," Steinhauser said. "The 10-year anniversary (of the tax) is in March 2014."